The following correction was printed in the Guardian's Corrections and clarifications column, Friday 17 April 2009

The article below about convictions for rape contained a miscalculation. It said that of an estimated 47,000 women raped in Britain each year, a minority - ranging from 5% to 25% - report the attack. When the conviction rate of 6.5% is correctly applied to that higher (25%) figure of reported rapes, the result is an estimated 764 successfully prosecuted cases out of 11,750 reported, rather than 191 as we stated. The author noted that only a quarter of reported complaints get to court, and to that lesser figure of 2,938 mistakenly applied the same conviction rate of 6.5%. This has been corrected.

I have only heard one person expounding at length that women regularly "cry rape" in order to enjoy a free ride home in a squad car after a night out. And he was a detective sergeant. Certainly, a tiny and overexposed minority do confect allegations. Many, many more do not. This is Britain in the spring of 2009. An estimated 47,000 women are raped in this country every year. Between 75% and 95% of them will never report their attack. Of those who do, only a quarter make it to court, and there face an abject conviction rate of 6.5%. By my most conservative calculations, this results in 764 of those 11,750 ever seeing justice done.

The trials of John Worboys and Kirk Reid, serial offenders let free to rape and rape again because of police incompetence, as well as the damning internal inquiry into the botched handling of a teenager's assault in Southwark, may have briefly focused attention on the treatment of sex crimes by the authorities - as today's Home Office announcement of more support for victims would suggest. But this is not about a few bad apples, isolated ineptness, or uniquely cunning perpetrators. It is happening every day to women whose stories won't make the front pages.

Nor is this about gender. There are just as many men outraged by what has happened to their partners or daughters - witness the desperate boyfriend who recently posted CCTV footage of his fiancee's attacker on Facebook, after police had failed to identify a suspect in eight months.

This is about systemic, institutionalised negligence. If you are raped, the likelihood is that the police won't help you, and the CPS won't help you. If you unusually achieve a trial, the prosecution won't help you and the judge won't help you. This is Britain in the spring of 2009, with a criminal justice system that delivers only one message to rapists: go ahead with impunity.

Over the past weeks, I have spoken to professionals, campaigners, survivors, and their mood has been consistently low. These recent high-profile cases change nothing when they are met with the same weary platitudes about energetic new initiatives and lessons learned. The new measures announced this morning appear to be little more than a recycling of recommendations already in place regarding training and best practice, although one proposal to regularly assess forces provides a modicum of cheer.

Most depressing of all is that these three investigations were conducted under the aegis of Project Sapphire, supposedly the country's flagship sex crimes unit. Yet, in its report on the Southwark debacle, the IPCC found that an untrained police constable had been left alone to deal with a workload that would have tested an experienced specialist, while the unit manager's unanswered pleas for more staff led her to conclude that greater importance was afforded to car crime than to victims of serious sexual assault.

"It's so bloody slow," an officer told me, the utter frustration evident in her voice. "We're still fighting for a uniform that comes in female sizes. That just typifies how the service deals with women." This is a sentiment echoed in other conversations: it's still impossible to discuss institutional sexism in the same way as institutional racism; the prevailing culture marks rape investigations as "grief", and no way to further your career; some brilliant programmes do exist, but go to the next borough and nobody's heard of them.

One survivor explained to me: "It's so simplistic. If you're a nice, white, middle-class woman, you might have a chance of being believed. But add in another factor - if you were drunk, or knew him, or you're a teenager, or a sex worker - and you don't stand a chance."

Beyond that dismal first response, the obstacles for a complainant remain enormous. The decision-making of the CPS is as tainted as that of the police. Those few women who find their allegations waved through to trial encounter further police failure to collect vital evidence, disengaged barristers, and arcane rules of court that prevent essential detail from being presented. "Everything is taken out of your hands," one told me. "You wonder why you're even there."

Meanwhile, juries are left to rely on the direction of judges - who often fail to explain new rulings on consent and the majority of whom continue to allow a victim's past sexual history to be examined, thanks to an invidious legal loophole. One juror described sitting on a rape trial as "trying to put together a jigsaw puzzle with half the pieces missing". The irony is that the police, CPS and judges love to blame juries for the appalling conviction rate. But their argument is evidently specious given so few cases ever reach that stage. The truth is that the public has progressed far beyond the criminal justice establishment in its attitude to sexual offences.

It is profoundly irritating that, whenever it seems there might be opportunity for a meaningful interrogation of this country's rape crisis, two perennial distractions hijack the debate. The first is the suggestion that conviction rates would be ameliorated by a tiered system of penalties, dividing stranger rapes from acquaintance rapes for example. It was even mooted in a Guardian leader column last year.

But rape is rape. The courts already have sufficient discretion in sentencing. To perpetuate the idea that an assault is not so traumatic because you were familiar with your attacker, or was less of a violation because you were anaesthetised by alcohol, would only make women even less likely to come forward, and bolsters the nonsense that anyone other than the victim herself is the best judge of the implications of her assault.

Second, the acquittal of a university student charged with raping a middle-aged lawyer, in the same week that Reid was found guilty, prompted familiar calls for anonymity to be extended to the accused in such cases. But legislation granting anonymity to alleged perpetrators was tested in the late 70s, then overturned when the police made it clear that it was depriving them of witnesses and hampering investigations.

Further tinkering with the law is not what is needed. We already have some of the best sex crimes legislation in Europe, but a judiciary that refuses to apply it, a police service that won't enforce it, and a government that is too otherwise occupied or too lazy to recognise that without prescriptive pressure from the top there is no incentive for change.

This is Britain in the spring of 2009. We are not some UN-designated failed state. We have a criminal justice system that operates reasonably effectively for pretty much everybody else. But 191 women this year will see justice done. And 46,809 will not. I refuse to believe that all of them are lying.